is it possible to backup third party applications from one bb bold and then somehow just copy one of the files over to another bb. i tried to copy the file into the pin folder, but when opening the alx file, it does not recognize the file copied. it is same format (no extension) as rest of other backed up apps.

No, you should definitely install all apps from the installation files, not copy them. There are lots of files that get installed in many hidden places. Missing just one of these could cause the app to fail completely.